1. Field of the Invention
The present invention relates to chain saw sharpening tools and more particularly to a chain saw sharpening tool which engages a saw chain and cutter bar and has a file holder which is guided during sharpening with respect to the cutter teeth of the saw chain by the portion of the tool which is engaged with the saw chain.
2. Description of the Prior Art
Many devices have been developed to aid a person in the sharpening of chain saw cutting teeth. Primarily, it is a question of orienting the file which sharpens the chain saw cutting teeth with respect to the cutting edges of those teeth and maintaining that orientation during the filing sharpening stroke of the file. First the file must be angulated in the horizontal plane with respect to the leading or cutting edge of the cutter tooth because the cutting edge is raked with respect to the forward movement of the tooth in the cutting bar of the saw chain. In addition, the file handle must be angulated in a vertical orientation as most teeth are formed with a sloping head which generally is a ten degree slope.
Thus, for a person to sharpen a tooth freehand without the aid of a guide or guage, the sharpening process is not accurately done by even those with a great deal of experience. It is just too difficult to hold both angles accurately for freehand sharpening. The problem is especially exacerbated when the angles must be reversed for each tooth as they alternate in their rake and slope with respect to the forward direction of the chain. Almost every person has a preferable orientation for stroking the file, either right-handed or left-handed, whereby changing orientation to the less preferred angles are not as accurately tracked during filing as during the preferred orientation.
In order to overcome these problems, many devices have been provided for aiding in the sharpening of saw chains. Some devices require the dismantling of the chain from the saw and placing each individual tooth in a vise which permits the file to be accurately tracked across the face of the tooth. Improvements on that type of a device have included sharpeners which clamp directly to the cutter bar of the saw chain and then sharpen each tooth as it is moved past the clamped-on device. However, accurately positioning teeth with respect to the cutter bar is difficult because the chain is not easily moved in the cutter bar due to its engagement with the motor. Thus, those types of devices must be moved back and forth which means attaching and detaching for sharpening each individual tooth.
Simpler devices have been developed which simply provide a reference angle for the file as it is being freehand-moved for sharpening the teeth. The advantage to these devices is that they are not clamped to the saw chain cutter bar and can be easily moved along the saw chain for filing each successive tooth without having to detach or disassemble the gauge. The problem is that these gauges do not provide an accurate positive engagement with the file holder for insuring that the file accurately tracks during the sharpening strokes.
The present invention overcomes the problems of each of these devices by providing a gauge which fits over the saw chain and cutter bar and is easily slid therealong without having to attach or detach it from either the chain or cutter bar. In addition, the guage engages the file holder to guide it during each stroke in repetitive tracking reciprocation. Further, the engagement means of the present invention allows easy and quick change engagement or disengagement of the file holder with the guide and also allows quick change reorientation of the guide with respect to the saw chain for alternating the angles of sharpening.